Device and method for inwardly transferring bulk material into a pneumatic conveyor line

ABSTRACT

In a device for transferring bulk material from a reservoir or a holding space through a lock space into a pneumatic conveyor line—in which the lock space can be closed in relation to the reservoir or holding space by an axially movable closure body and at least one counterpart sealing element disposed in opposite relationship in its path of movement—the closure body has at least one vent opening which opens into an air discharge passage and can be closed in the upward closing movement of a stroke element with the sealing body; the downward opening travel (x) thereof is shorter than the downward travel of the stroke element with the sealing body. The closure body enlarges from a narrow cross-section—forming an inner sealing edge in a funnel-like configuration towards the sealing body and the narrow cross-section is an annular seat for the sealing body in the closure position. One of the counterpart sealing elements is a flexible sealing surface which is gripped in respect of cross-section at one end and the other is a sealing edge which entrains the free edge region thereof and which increasingly deforms it in the path of movement; the sealing surface is preferably in the form of a ring surrounding the closure body.

The invention concerns a device and a method of transferring bulkmaterial from a reservoir or a holding space through a lock space into apneumatic conveyor line, wherein the lock space is closable in relationto the reservoir or holding space by a movable closure body and at leastone counterpart sealing element in opposite relationship thereto in itspath of movement.

Devices of that kind are to be found in EP 0 166 959 B1; at its intakeside it has a conical closure body, in the center of which a ventopening surrounded by a resilient collar is cyclically closed and openedby a stepped cone of elastic material. The seal which is disposed inopposite relationship to the closure body is to be deformed by theconveyor air which is supplied thereto—through an annular passagedisposed therebeneath—in such a way that the conveyor air issuesuniformly directed on to the closure body and thus in the closuremovement blows the closure body—seal contact line free of product. Thatis intended to ensure a pressure-tight sealing action for the inner lockspace towards the supply reservoir. Release of the compressed air at theend of the conveyor cycle is effected directly by the now open centralopening in the closure cone into the supply reservoir which is disposedthereabove and which is filled with the product to be transported. Theair has to flow through the pores of the product.

It has been found that the distribution of air through the deformableseal is not so uniform that the closure body always closes against thesealing edge of the seal in pressure-tight relationship. In additionwith strain gauge measurements made on the walls of the reservoir it wasestablished that the discharge air which flows through the pores in theproduct, when the reservoirs are of considerable height—for example insilos—builds up pressures which make it necessary for those containersto be of a relatively great wall thickness, which thus involves highercost levels.

That deficiency was overcome by the invention described in EP 0 270 012B1, insofar as the air released from the lock space is passed through atube portion at the closure cone with an opening arranged above the flowpath of the bulk material, into an intake housing, and is dischargedthrough a central opening in the intake housing. When the pressure inthe lock space has fallen, the closure cone moves downwardly and theopening in the tube portion is closed in that position of the closurecone by a resilient cone tip. The opening is only open in the airrelease procedure; both in the conveyor mode of the apparatus and alsowhen the bulk material is passing into the lock space, the opening isclosed by the resilient cone tip. Therefore the air which is displacedby the bulk material as it flows into the lock space must be passed incounter-flow relationship through the inwardly flowing bulk material.That increases the length of the period of time required to fill thelock space.

A not inconsiderable duration for the filling operation is also involvedin the arrangement of EP 0 166 951 B1. In that case, provided beneaththe closure element for the outlet of the lock space is a feed line forconveyor air. The major part of the conveyor air enters here, atrelatively high flow speed, due to the small cross-section involved.There is a pressure drop in the discharge housing, due to the flow beingaccelerated in the cross-section of the mouth opening. In a condition ofco-operation with the product-air mixture which subsequently flows outof the lock space and which is discharged through the conveyor conduit,that produces an upward and downward movement of the discharge flap. Asa result, the switch actuated by the discharge flap initiates ventoperations before the lock container is completely emptied. Wear occursin the discharge air lines and there is a loss in conveyor capacity dueto the fact that the bulk material does not entirely discharge from thelock space. If the air feed is arranged about 3 meters downstream on theconveyor line, the described effect is eliminated, as can be seen fromEP 0 270 012 B1. As in that case however the transport of product fromthe discharge housing to that air feed-in location only has to beovercome by the amount of air added at the closure head at the intakeend, the conveyor capacity is reduced.

The conveyor capacity to be achieved depends on the duration of thecycle time. The cycle time is primarily composed of the emptying timeand the filling time of the lock space. The emptying time issubstantially dependent on the properties of the bulk material, theconveyor path, the conveyor cross-section, the conveyor air speed andthe conveyor pressure. The filling time of the lock space is in turnsubstantially determined by the properties of the bulk material, thefeed flow cross-section, the open cross-section of the closure head andthe flow conditions in the opened closure head when the bulk material isflowing into the lock space. It has been found that the introduction ofbulk material takes place reliably and quickly only with relativelygrainy and heavy bulk materials, for example quartz sand and sugar incrystal form. In the case of light bulk materials in dust form theintroduction thereof is uncertain and the introduction time is very longso that these devices do not achieve adequate conveyor capacities.

The device disclosed in EP 0 270 012 B1 also provides that lightmaterials to be conveyed are fluidised in the intake housing by the airwhich rises in counter-flow relationship, and substantially fill theintake housing. Upon next venting of the lock space considerable amountsof the material to be conveyed are then discharged through the centralopening of the intake housing. In practice those amounts of conveyor airin those apparatuses can be fixedly set by means of adjustable throttlevalves; there is no regulation of the pressure and loading conditions ofthe conveyor flow. As a result it is not possible to make optimum use ofthe energy of the conveyor air which is introduced into the system.Sealing elements of elastic material are required in the known devicesfor permanently pressure-tightly closing off the lock space. Theadmissible temperature range is greatly restricted by the properties ofthose materials.

With knowledge of that state of the art the inventor set himself the aimof providing a simple device and a conveyor method for same, with whichthe levels of conveyor capacity can be increased and even light bulkmaterials in dust form can be transferred into a conveyor line. Theinvention further seeks to provide that the conveyor operation is moreeconomical and even hot materials being conveyed can also be fed into aconveyor line.

The teaching of the independent claim provides for attainment of thatobject; the appendant claims set forth advantageous developments. Thescope of the invention also embraces all combinations of at least two ofthe features disclosed in the description, the drawing and/or theclaims.

In accordance with the invention the closure body has at least one ventopening which opens into an air discharge passage and is closable uponthe upward closing movement of a stroke element with a sealing body; thedownward opening movement thereof is also shorter than the downwardmovement of the stroke element with the sealing body. In that respect ithas proven to be desirable for the closure body to be so designed thatit enlarges from a narrow cross-section forming an inner sealing edge ina funnel-like configuration towards the sealing body and the narrowcross-section is an annular seat for the sealing body in the closureposition.

In accordance with further features of the invention an air dischargepassage is taken from the vent opening of the closure body to anaperture in an intake housing which is arranged upstream of the lockspace, and the air discharge passage is connected to an air dischargeline at the aperture in the operative condition. In addition the sealingbody should be provided with a conical tip for the annular seat.

The closure body which is provided at the intake end in the lock spaceand which seals against a peripherally extending edge in the closureposition therefore has at least one vent opening which opens into an airdischarge passage and is closed in the upward closing movement with thesealing body.

By virtue of that arrangement the air which is displaced out of the lockspace by the inflowing bulk material can leave the lock space throughthe vent opening of the closure body without retarding the inflowingbulk material. If in addition air is sucked away at the intake housingwhen the bulk material passes into the lock space, the discharge of airfrom the lock space is accelerated and thus the bulk material intaketime is further reduced. Particularly for light bulk materials of finegrain size, it is advantageous for the vent opening in the closure bodyand the air outlet opening of the intake housing to be connectedindependently of travel. In accordance with the invention that can beeffected for example by means of a concertina member or by hollowprofile members which are guided telescopically one within the other. Byvirtue of those features discharge of the air takes place in the optimumfashion and the required bulk material intake time is very short. Thosepassages can easily be so designed that—as stated—the possible openingtravel of the closure body is less than the opening travel of the strokedrive.

Fans but in particular injectors which can very advantageously bearranged in an air discharge passage are suitable for discharging theair. A suitable form of stroke drive is in particular—per seknown—pneumatically actuated bellows-type cylinders and double-actingpneumatic cylinders whose upward and downward movement is produced byair acting alternately on the two piston surfaces, but alsosingle-acting pneumatic cylinders with a plunger piston. In thearrangement with a plunger piston the closing movement is effected bymeans of compressed air, while the opening movement is produced eitherby the weight of the plunger piston and the closure body or by virtue ofa reduced pressure being applied to the piston surface. The openedposition is then achieved by a suction effect on the plunger piston.

It is possible to combine with that device arrangements—for example pinsand guides—which rotate the closure body somewhat about its axis in itsupward/downward movement. In that way the contact surfaces of theclosure body and the peripherally extending sealing edge are permanentlysmoothed, kept groove-free and permanently remain sufficiently capableof affording sealing integrity, even if the closure body and theperipherally extending sealing edge comprise tough material, for examplesteel. That affords a design configuration of the device according tothe invention even for hot bulk materials. If the seal which forms theperipherally extending sealing edge comprises elastic material, it canbe so designed that the closing movement of the closure body is at leastin part converted into a reinforcement of the sealing action. By virtueof that design configuration it is possible to produce markedly simplerdevices—in particular for introducing substances in granule form intopneumatic conveyor lines—than is possible with the devices in accordancewith the state of the art.

As is known, the feed of conveyor air can be effected on the one handinto the lock space through an air curtain which is directed on to theclosure body and on the other hand, as viewed in the flow direction,downstream of the discharge cross-section of the lock space. If a valveis also present at the lock space outlet cross-section, then inaccordance with the invention an air curtain can also be directed hereon to the sealing edges of the valve for the purposes of cleaning thosesealing edges. That is particularly advantageous when that valve is of atough nature.

In accordance with the invention the feed of the conveyor air downstreamof the valve should be implemented over a large area. In that wayfluctuations in pressure emanating from the fed-in conveyor air in thatregion are avoided. In accordance with the state of the art, the two airflows can be set by means of throttle valves or aperture devices. It ishowever more advantageous, in accordance with the invention, to controlthe two air flows in accordance with the fluctuating pressure in thelock space or at the beginning of the conveyor line; in that way it ispossible to make optimum use of the energy of the supplied compressedair.

Until a preselected conveyor pressure is reached, compressed air isprimarily fed to the lock space, then to the air feed-in location whichis downstream of the lock space, until the conveyor pressure has fallenbelow the preselected conveyor pressure. That provides that the ratio ofthe amount of material being conveyed to the amount of conveyor air isalways kept almost at the optimum, while for a proportionate air flowthe air feed-in locations can be connected by passages.

Particularly when dealing with materials to be conveyed which have apoor capacity for resistance to air, it is advantageous to couple an airin-feed at the beginning of the conveyor pipe, to the air in-feed at thevalve which is connected downstream of the lock space. It is alsopossible to use a plurality of air feed-in locations along the conveyorline, which are controlled from the device according to the invention.Switching of the air in-feed can be effected pneumatically orelectropneumatically.

It is also in accordance with the invention, in a device as set forth inthe opening part of this specification for introducing bulk materialfrom a reservoir or a holding space through a lock space into apneumatic conveyor line—in which the lock space is closable in relationto the reservoir or holding space by an axially movable closure body andat least one counterpart sealing element disposed in oppositerelationship thereto in its path of movement—for one of the counterpartsealing elements to be in the form of a flexible sealing surface whichis clamped in cross-section at one end and for the other to be in theform of a sealing edge which entrains the free edge region of thesealing surface and increasingly deforms it in the path of movement;that sealing surface should preferably be a ring surrounding the closurebody. Protection is claimed separately in respect thereof, and inrespect of a design configuration in which the sealing surface is asealing lip which is clamped in cross-section at one end on the housingside and the closure body is provided with at least one projectingsealing edge and with at least one entrainment portion which engagesunder the sealing lip. That thus affords an extremely efficient andsimple sealing region.

The feature of inwardly deforming the lower edge region of the closurebody which enlarges funnel-like in opposition to the stroke direction,forming the sealing edge and an inclined edge portion, makes it possibleon the one hand easily to produce the required sealing edge and on theother hand to afford on the inclined edge portion the entrainmentportions which then project therefrom.

In accordance with another feature of the invention the thickness of thesealing lip is greater than the spacing of the entrainment portion orportions from the sealing edge so that same can engage into the lip edgeafter the edge region has been lifted by the entrainment portions.

In another embodiment the deformable seal is part of the closure bodyand its lip edge is directed towards the edge of a stationary opening inthe device.

At any event it has proven to be desirable for the sealing lip to beclamped at one end between two flanges. In addition the sealing lip isto be inclined downwardly in cross-section at an angle from its clampinglocation so that its lip edge faces in opposite relationship to thestroke direction. The latter moreover in the relieved position of thesealing lip is to extend substantially parallel to the stroke travel orthe longitudinal axis of the device.

The method according to the invention is distinguished in that airdisplaced from the lock space during the inward transfer of the bulkmaterial is discharged through at least one vent opening in the closurebody, which goes into an air discharge passage. The displaced air canalso be sucked out of the lock space. It has proven to be advantageousfor the conveyor air to be fed to the described device at at least twofeed-in locations and for those feed-in locations to be controlledalternately in dependence on a predetermined reference value of theconveyor pressure and an instantaneous actual value of the conveyorpressure.

Further advantages, features and details of the invention will beapparent from the description hereinafter of preferred embodiments andwith reference to the drawing in which:

FIG. 1 is a view in longitudinal section through a device fortransferring bulk material into a pneumatic conveyor line in the intakeposition,

FIG. 2 shows a part from FIG. 1 on an enlarged scale,

FIG. 3 is a view corresponding to FIG. 1 of another embodiment of thedevice which is particularly suitable for hot bulk materials,

FIG. 4 shows a part of FIG. 3 on an enlarged scale,

FIG. 5 shows a view on an enlarged scale in comparison with FIG. 1 of adetail of an embodiment of a sealing system on a device for conveyingsubstances in granule form, in two half-sections of mutually differentoperating positions, and

FIG. 6 shows a control diagram relating to the feed of conveyor air intothe device.

A device 10 for the transfer of bulk material (not shown in the drawing)into a pneumatic conveyor line 12 has, by way of a connecting bend 18ending at a flange portion 14 with an annular gap nozzle 15 togetherwith a compressed air connection 16, a base portion 20 of a lock housing22, the base portion 20 tapering conically towards the connecting bend18. The lock housing 22 encloses a cylindrical lock space 24 of aninternal height h, at the upper end of which on the one hand there isprovided a pressure measuring device 26, and on the other hand a maximumlevel probe 27 extends thereinto; an empty probe is indicated at 28 inthe base portion 20.

Resting on an upper annular flange 23 of the lock housing 22 is anannular flushing flange or housing cover 30 which at its inner annularedge is provided with a blowing device 32; a radial compressed airconnection 33 extends therefrom.

A tower-like intake housing 34 is fixed on the housing cover 30 withscrew bolts 35, the intake space 36 thereof, which forms a holdingspace, being bridged across by a top wall 38. The latter includes at acentral aperture 40 an injector 41 with a compressed air feed line 42.The aperture 40 which is on the longitudinal axis A of the housing alsopasses through a connecting flange 44 which sticks up from the top wall38, for an air discharge line (not shown). A feed pipe 46 which isinclined upwardly from the intake space 36 for the bulk material openslaterally into the intake space 36.

Bolt-like round bars 48 project from the housing cover 30 in parallelrelationship with the axis into the lock space 24. At the other end, acarrier plate 50 which is arranged at the upper edge of the base portion20, for a stroke element 52 which is variable in respect of height, isconnected to the round bars 48; the stroke element 52 is for example inthe form of a bellows-type cylinder into which opens an air connection54 which can be seen beneath the carrier plate 50.

The bellows-type cylinder 52 axially carries a cylindrical sealing body56 of a diameter d with an upwardly projecting cone tip 57. Supports 58project radially on both sides thereof from the round bars 48—at aspacing i in relation to the housing cover 30.

An air discharge passage 60 in the form of a bellows member is fixed tothe underside of the top wall 38—surrounding the central aperture 40thereof. The bellows member goes downwardly at a cylindrical ventopening 62 with a conically enlarging annular seat 63 for the cone tip57, into a closure or funnel-shaped body 64 which enlarges conicallyfrom the annular seat 63 and whose funnel edge 66 rests on the supports58; they delimit the opening travel of the closure body 64 in thedirection indicated by the arrow x.

Provided between a sealing edge 70 which can be seen at the top side ofthe housing cover 30 and which is provided by an insert ring 71 of theintake housing 34 and the closure body 64 is an outer annular intakecross-section 72 of a width b, through which the bulk material flowsinto the lock space 24.

In the lower position of the sealing body 56 as shown in FIG. 1, a ventgap 74 is formed between the sealing body 56 and the closure body 64(see FIG. 2).

In the illustrated embodiment in FIGS. 1 and 2 the closure body 64 andthe air discharge passage 60 are made in one piece with insertedreinforcing inserts 68 from wear-resistant elastic material. As a resultthe sealing edge 70 and the sealing body 56 can comprise hard material.The lock device 10 operates cyclically. In the illustrated filling phasethe bulk material flows through the intake housing 34 and the intakecross-section 72 into the empty lock space 24. The air displaced by thebulk material is passed—assisted by the injector 41 fed by thecompressed air feed line 42—in an intensified fashion, in oppositerelationship to the direction indicated by the arrow x, through the ventgap 74 and the air discharge passage 60 to the air discharge line whichcan be connected to the connecting flange 44.

After the maximum level probe 27 responds or after the expiry of anadjustable filling time the bellows-type cylinder 52 is acted upon bycompressed air, by way of the air connection 54. It lifts the sealingbody 56 against its annular seat 63 on the closure body 64 and thuscloses off the air discharge path. In its further stroke movement thebellows-type cylinder 52, by means of the sealing body 56, lifts theclosure body 64 against the peripherally extending sealing edge 70 andthus closes off the way into the intake housing 34, for the conveyor airwhich is supplied at the same time through the blowing device 32. Theconveyor pressure builds up in the lock space 24. The bulk material isfed to the annular gap nozzle 15 and conveyed away through the conveyorline 12, with the compressed air which is discharged at the nozzle 15 atthe same time.

When the lock space 24 is empty that is detected by the empty probe 28.When the conveyor line 12 is finally free of bulk material, that isdetected by the pressure measuring device 26, due to the pressure drop.One of the two signals is used to initiate the release of compressed airin the bellows-type cylinder 52.

The bellows-type cylinder 52 is reduced in length, and the vent gap 74is formed at the sealing body 56, in relation to the annular seat 63 ofthe closure body 64. The residual pressure from the lock space 24 canescape to the air discharge conduit. After the reduction in pressure inthe lock space 24 the closure body 64 drops on to the supports 58 andthereby again opens the intake cross-section 72. The vent cross-section74 remains open and fresh bulk material can flow in. The air displacedby the bulk material in the lock space 24 is drawn off by the injector41.

In the view of the enlarged portion shown in FIG. 2 it is possible tosee in particular the open vent gap 74 which extends between the annularseat 63 of the closure body 64 and the cone tip 57 of the sealing body,through which the air displaced by the inflowing bulk material can flowaway unimpededly.

The stroke element of the device 10 _(a) shown in FIG. 3 is in the formof a pneumatic cylinder 52 _(a) which is disposed coaxially in front ofthe funnel shaped or closure body 64 _(a) and which has a plunger piston53, being extended upwardly into the upwardly conical sealing 56 _(a).For the upward movement of that plunger piston 53 compressed air ispassed through the connection 54 into the pneumatic cylinder 52 _(a),while for the downward movement a reduced pressure is applied to theconnection 54. In its upward movement the sealing body 56 _(a) closesthe vent cross-section or gap 74 which goes into the air dischargepassage 60 _(a) which here is in the form of a hollow profile of anoutside diameter e, while in the opened position of the device 10 _(a),it rests with an external bead or ridge 76 at its end—as shown in FIG.4—on an internal collar 78 of a hollow head profile member 61 of largeroutside diameter e₁, which projects downwardly from the top wall 38. Byvirtue of that configuration, the vent cross-section 74, in the openedposition of the device 10 _(a) in which the bulk material flows into thelock space 24, on the one hand is kept open, while on the other hand theclosure body 64 _(a) is freely movable until, in its closing travel inthe direction y, it reaches the peripherally extending annular seat 63acting as a sealing edge, and thus closes off the lock space 24 towardsthe intake housing 34.

Arranged at the outer periphery of the closure body 64 _(a) are inclinedguide surfaces which, by means of projections 58 _(a) protruding fromthe round bars 48, rotate the closure body 64 _(a) stepwise about thelongitudinal axis A of the housing, in the axial vertical movement ofthe closure body 64 _(a). That results in the elimination of partialleakages which can occur for example due to the formation of grooves orfurrows at the sealing edge 70. That is particularly advantageous when,when dealing with hot bulk material, the sealing edges 70 must comprisetough, heat-resistant material.

In this case, the blowing device 32 for producing the air curtain whichis directed towards the closure body 64 _(a) is in the form of anannular nozzle with tangential air in-feed through the connection 33_(a). The conveyor line 12 with the annular gap nozzle 15 can beuncoupled from the lock space 24 by means of an outlet valve 82 in theconnecting bend 18 _(a). Diagrammatically shown in the lock space 24 at80 is a porous cone with an air connection 81, by which the discharge ofmaterial being conveyed out of the lock space 24 is assisted.

The discharge valve 82 is for example provided with a conical closurehead 84 having a plunger piston 54 _(a). The seat 86 of the dischargevalve 82 is blown free of product in the closing operation by means ofan air curtain, by means of an annular gap nozzle 88 with a tangentialflow thereto. Other types of valves—for example slider members orflaps—can also be used as the discharge valve.

The closure head 84 is moved alternately in relation to the closure body64 _(a). In that way, it is possible to maintain the conveyor operationin the conveyor line 12 when the lock space 24 is in the pressure-lesscondition, when the feed of compressed air still occurs through theannular gap nozzle 15 of the flange portion 14.

A particularly advantageous embodiment of the sealing system between theintake housing 34, the lock space 24 and the closure body 64—like also64 _(a)—and the functioning thereof is shown in FIG. 5, in twohalf-sections. The left-hand half in FIG. 5 shows the lower position ofthe closure body 64 on its closing travel y at a seal or sealing lip 90with a lip edge 91 which here is parallel to the axis, the seal orsealing lip being gripped in a pair of flanges 89 of the lock housing 22and the intake housing 34, inclined at an angle of inclination w ofabout 40°. The right-hand half of FIG. 5 shows the upper position of theclosure body 64, providing for sealing closure between the intakehousing 34 and the lock space 24.

That sealing system comprises the closure body 64 with an air dischargepassage 60 which extends upwardly therefrom, the stroke element 52 andthe resilient seal 90. The closure body 64 which enlarges downwardly ina funnel-like configuration has an edge portion 95 which is curvedinwardly in respect of its cross-section—at a sealing edge 94—and fromwhich pin-like entrainment portions 92 project radially. The spacing zthereof from the sealing edge 94 is shorter than the thickness t of theseal 90. In the stroke movement of that closure body 64 of a maximumoutside diameter n, the entrainment portions 92 engage under the seal 90in such a way that the edge region thereof is entrained upwardly and theinside diameter q thereof is reduced; the lip edge 91 of the seal 90bears snugly against the peripherally extending sealing edge 94, as isshown in a somewhat exaggerated form in FIG. 5 for the sake of enhancedclarity. Tests have shown that it is sufficient if the sealing edge 94penetrates into the seal 90 by only fractions of a millimeter.

The deformation characteristics of the seal can be determined in theoptimum fashion by virtue of the configuration of the seal 90 and/orreinforcement thereof.

The system also makes it possible for the deformable seal 90 to be inthe form of part of the closure body 64—this is not shown—; it movesinto a fixed opening and is there deformed in such a way that itsoutside diameter is increased and thus produces a sealing closure effectin the opening.

In a particularly advantageous manner of air feed-in control for thelock device 10, 10 _(a), as shown in FIG. 6, compressed air flows from acompressed air source 96 through a line 97 to a comparator 98. A feedline 100 also opens thereinto, the feed line 100 being acted upon by theactual conveyor pressure of the lock device 10, 10 _(a) (not shown inFIG. 6), with a conveyor pressure which is predetermined at a referencevalue generator 102 through a feed line 100 _(a).

Compressed air lines 104 and 104 _(a) are connected to the outlet of thecomparator 98; the compressed air line 104 goes to the connection 33 ofthe blowing device 32, possibly to the connection 81 of the porous cone80 (FIG. 3). The compressed air outlet 104 _(a) is associated with theannular gap nozzle 15 of the flange portion 14 and can be taken toconnections along the conveyor line 12. Both compressed air lines 104,104 _(a) are connected together in quantitatively limited relationshipby a throttle section 106.

The comparator 98 switches the outgoing compressed air lines 104, 104_(a) alternately in such a way that—if the actual conveyor pressure atthe feed line 100 is equal to or greater than the pressure which ispredetermined by the reference value generator 102—the compressed airwhich is being supplied through the line 97 is fed to the outgoingcompressed air line 104 _(a). If the actual conveyor pressure at thefeed line 100 is less than the reference conveyor pressure at the feedline 100, the compressed air is switched to the outgoing compressed airline 104.

The comparator 98 can directly process pneumatic signals or electricalsignals if the signal supplied through the feed line 100 is convertedinto an electrical signal and the reference value signal ispredetermined electrically.

What is claimed is:
 1. A device adapted for transferring bulk materialfrom a holding space through a lock space into a pneumatic conveyorline, wherein the lock space is closable in relation to the holdingspace by an axially movable closure body and at least one counterpartsealing element in opposite relationship thereto in its path ofmovement, characterised in that the closure body has at least one ventopening which opens into an air discharge passage and is closable in theupward closing movement of a stroke element and a sealing body, whereinthe downward opening travel (x) of the sealing body against the closingmovement is shorter than the downward travel of the stroke element withthe sealing body.
 2. A device as set forth in claim 1 characterised inthat the closure body (64, 64 _(a)) is enlarged from a narrowcross-section forming an inner sealing edge (63) towards the sealingbody (56, 56 _(a)) in a funnel-like configuration and the narrowcross-section is the annular seat for the sealing body in the closureposition.
 3. A device as set forth in claim 1 characterised in that anair discharge passage (60; 60 _(a), 61) goes from the vent opening (62)of the closure body (64, 64 _(a)) to an aperture (40) in an intakehousing (34) arranged upstream of the lock space (24) and the airdischarge passage can be connected at the aperture to a discharge airline.
 4. A device as set forth in claim 1 characterised in that thesealing body (56, 56 _(a)) is provided with a cone tip (57) for theannular seat (63).
 5. A device as set forth in claim 1 characterised inthat in the region of its vent opening (62) the closure body (64, 64_(a)) is connected to an air guide element (60; 60 _(a), 61) which isvariable in length, as an air discharge passage.
 6. A device as setforth in claim 5 characterised by a bellows member (60) as the air guideelement.
 7. A device as set forth in claim 1 characterised in thatdisposed in opposite relationship to the lower edge (66) of the funnelconfiguration of the closure body (64, 64 _(a)) are abutment elements(58, 58 _(a)) provided in the lock space (24).
 8. A device as set forthin claim 3 comprising a reduced pressure source (41) at the airdischarge passage (60; 60 _(a), 61), at which an injector (41) isarranged.
 9. A device as set forth in claim 1 characterised in that theclosure body (64, 64 _(a)) which is movable in the lock space (24) issurrounded by a substantially stationary sealing edge (70, 91) as acounterpart sealing member.
 10. A device as set forth in claim 9characterised in that a blowing device (32) for producing an air curtainis associated with the sealing edge (70, 91) and the closure body (64,64 _(a)).
 11. A device as set forth in claim 10 characterised in thatthe blowing device (32) is in the form of an annular gap nozzle with atangential air feed (33).
 12. A device as set forth in claim 10characterised in that the sealing edge and the blowing device arearranged in the transitional region between the intake housing and thelock space.
 13. A device as set forth in claim 11 characterised in thatthe blowing device (32) with its air feed (33) forms a separate annularinsert between the intake housing (34) and the lock housing (22).
 14. Adevice as set forth in claim 1 characterised in that a conveyor airpartial flow introduction means (15, 16) is arranged downstream of thelock space (24) at its outlet.
 15. A device as set forth in claim 1characterised in that the stroke drive for the sealing body (56)comprises a bellows-type cylinder (52).
 16. A device as set forth inclaim 15 characterised in that the bellows-type cylinder (52) isarranged on a carrier plate (50) in the lock space (24).
 17. A device asset forth in claim 1 characterised in that connected to a compressed airsource (96) is a comparator (98) to which there are connected a feedline (100) for conveying the actual conveyor pressure of the lock device(10, 10 _(a)) and a feed line (100 _(a)) from a reference valuegenerator (102).
 18. A method of transferring bulk material from areservoir or a holding space through a lock space into a pneumaticconveyor conduit by means of a device adapted for transferring bulkmaterial from a holding space through a lock space into a pneumaticconveyor line, wherein the lock space is closable in relation to theholding space by an axially movable closure body and at least onecounterpart sealing element in opposite relationship thereto in its pathof movement, characterised in that the closure body has at least onevent opening which opens into an air discharge passage and is closablein the upward closing movement of a stroke element and a sealing body,wherein the downward opening travel (x) of the sealing body against theclosing movement is shorter than the downward travel of the strokeelement with the sealing body characterised in that air displaced fromthe lock space during the introduction of the bulk material isdischarged through at least one vent opening in the closure body whichgoes into an air discharge passage.
 19. A method as set forth in claim18 characterised in that the displaced air is sucked out of the lockspace (24).
 20. A method as set forth in claim 18 characterised in thatthe conveyor air is fed to the device at at least two feed-in locationsand said feed-in locations are controlled alternately in dependence on apredetermined reference value of the conveyor pressure and aninstantaneous actual value of the conveyor pressure, wherein airin-feeds into the conveyor line connected downstream of the device arepossibly coupled to the conveyor air in-feed connected downstream of thelock space.
 21. A device as set forth in claim 15 characterized in thatthe pneumatic cylinder is arranged on a carrier plate in the lock space.